Longitudinal-control system for aircraft



Z44. AtHUNAUHUb W-. S. BURGESS. LONGITUDINAL CONTROL SYSTEM FOR AIRCRAFT.

APPLICATION FILED MAY 14. NH].

mmmboz WILLIAM STAELINe Bunzsasfi- 3 SHEETS-SHEET 2.

Patented Feb. 15, 1921.

W. S. BURGESS. LONGiTUDINAL CONTRQL SYSTEM FOR AIRCRAFT.

APPUCATION FILED MAYM. 19H.

Patented Feb. 15, 1921.

3 SHEETSSHEET 3.

WILLIAM QTAELING BUIZGB55- HEHUNHU l [U UNITED STATES PATENT OFFICE.

WILLIAM STARLIN'G BURGESS, OF MARBLEHEAD, MASSACHUSETTS, ASSIG-NOR T0 CURTISS'AEROPLANE AND MOTOR CORPORATION, A CORPORATION OF NEW YORK.

LON GITUDINAL-CONTROL SYSTEM FOR AIRCRAFT.

To all 20 ham it may concern:

Be it known that I, \VILLIAM STARLING BURGESS, a citizen of the United States, residin at Marblehead, in the county of Essex and btate of Massachusetts, have invented certain new and useful Improvements in Longitudinal-Control Systems for Aircraft, of which the following is a specification.

My invention relates to aeroplanes and more particularly to aeroplanes of the Dunne type-a type embodying swept back wings in which lateral stability is inherent and directional control obtained through manipulation of control surfaces mounted at the wing tips.

As an object of the invention it is proposed to provide a means for increasing the angle of attack of one of the supporting surfaces of a biplane or multiplane without correspondingly altering the angle of attack of the other or others. More especially it is proposed to limit this alteration of the angle of attack to the inner portions of the upper surfaces, which, in the Dunne type machine, constitute that portion of said surface in the vicinity of the apex formed by the swept back wings. A variation in the dcalage which widens the gap at the leading edge of the superposed wings is desirable and advantageous for several reasons: first, the power of the longitudinal controls is greatly augmented; second, all tendency to nose dive is completely eliminated, and finally, the climbing efficiency, during such time as the gap is widened, is increased proportionately to the increase in the angle of attack. Moreover, the gliding angle, when volplaning, may be decreased or appreciably reduced.

Another and correlated object of the invention is to provide for variation in the angle of incidence of the upper surface through manipulation of elevator flaps. These flaps are disposed preferably at the respective rearward terminals of the lower wings. Both said flaps and the inner portions of the upper wings are connected to the control column of the craft for operation through fore and aft oscillation of said column. Through this arrangement the variable dcalage and elevator flaps conj ointly function in strengthening longitudinal control.

A still further object of the invention is to provide in a Dunne type machine both elevators and rudders, segregate them, and mount the elevators at the tips of the lower Serial No. 168,587.

wings and the rudders at the tips of the-upper wings in unalined vertical planes.

In the drawings, wherein like characters of reference designate like or corresponding parts:

Figure l is a side elevation of a craft embodying the present invention;

Fig. 2 is a front end elevation illustrating in dotted lines the degree of warp or distortion which the upper wings are capable of receiving;

Fig. 3 is a top plan view of the craft as illustrated in Fig. 2;

Fig. 4 is a section on the line 44l of Fig. 3;

Fig. 5 is a detail elevation of the control column;

Fig. 6 is a fragmentary view illustrating in detail one of the spring stays;

Fig. 7 is a perspective view illustrating a modified wing structure, and

Fig. 8 is an elevation of the modified control mechanism.

The nacelle or body of the craft is designated in its entirety by the numeral 10. At its forward end it is equipped with a pilots cockpit l1 and at a point intermediate its ends with a passengers cockpit 12, the space intermediate the cockpits accommodating the variable load. Aft of the cockpit 12, the power plant 13 is disposed, the forward end of the power plant lying in the transverse vertical plane of a line projected through the center of gravity CG.

Although equally as well adapted for use upon land machines, I have illustrated the invention in connection with a hydroaeroplane in which a single pontoon 14 is arranged beneath the nacelle. Chassis struts 15 provide a mounting for the pontoon, the struts being preferably arranged in pairs for anchorage respectively adjacent to the sides or lateral margins of the pontoon and the nacelle. The pair of struts located foremost extend forwardly and downwardly at an angle and the pair rearmost substantially vertically. The intermediate pairs of struts converge downwardly as illustrated in Fig. 1 to provide with the fore and aft struts a rigid pontoon mounting. A rearwardly facing step 16, located in the transverse vertical plane of the center of gravity terminates abruptly the hydroplaning bottom of the pontoon. From the step aft, said bottom is non-hydroplaning in form.

The supporting surfaces of the craft are superposed, staggered and swept back, the wings 19 constituting the upper supporting surface extending laterally beyond the wings 2O constituting the lower supporting surface. The tips of the lower wings 20 are extended rearwardly in a fore and aft direction as indicated at 21 to terminate in a Vertical plane rearwardly beyond the corresponding terminal of the upper wings (see Fig. 3). Not only is the wing surface augmented by thus extending the lower wings but longitudinal stability increased. Moreover, provision is made for the disposition of both elevator flaps and rudder flaps at the wing tips in unalined vertical planes. The elevator flaps designated 22 and the rudder flaps designated 23 are hinged respectively at the tips of the lower wings 20 and the upper wings 19. Both are provided with an overhang. The rudder flaps 23 function as directional control surfaces in steering the craft to either the right or left and the elevator flaps 22 as directional control surfaces in steering the machine either up or down. The surfaces may be operated either independently or in unison.

The inner portions of the upper wings 19 are pivoted, the pivotal axes lying below said wings on lines somewhat aft of the center of lift. A tubular wing spar 24 parallels the axis of adjustment of each wing. This spar 24, in the vertical plane of the several wing posts 25, is equipped with rigidly united supports 26. These supports penetrate'the underneath surface of the upper wings for contact with wing posts 25. The connection between each support and its associated wing post 25 is pivotal in its nature. Each wing post 25 comprises mating wing post struts arranged to converge upwardly for seating engagement in a socket 27 common to both. The opposite terminals of the mating struts are fastened by any suitable means to wing spars 28 and 29 of the lower wings.

Limit stops, designated as an entirety by the numeral 30, in the nature of spring stays, define the degree of pivotal movement of the inner portions of the upper wings, the tension of the respective stays opposing the force obtained by the relative disposition of the pivotal axes with respect to the center of lift. These limit stops or spring stays 3O normally maintain the upper wings 19 at a determined angle of attack, preferably two or three degrees greater than the angle of attack of the lower wings 20. Said stays 30 are arranged to unite the adjacent ends of tie wires 31 (in place of turnbuckles) anchored respectively to the upper wings 19 adjacent the leading edges and the lower wings 20 in the plane of the forward wing beams 28. Movement of the inner portions of the upper wings 19 against action of the several spring stays 30 to increase the angle of attack of said upper wings is obtained through manipulation of the control column 32. This column 32 is mounted for fore and aft oscillation within the forward cockpit 11 of the nacelle, its axis of oscillation being determined by a shaft 33 herein referred to as the control column shaft. Said shaft 33 is equipped with a lever 34 rigid with it and movable in response to fore and aft oscillation of the column. Connections 35 are provided between said lever 34 and the inner portions of the upper wings, the connections engaging with the lever at points distant from its axis of oscillation proportional to the degree of warp or distortion to be given that portion of the wing to which the particular connection is fastened. These connections 35 extend rearwa-rdly from the lever 34, interiorly of the nacelle to a pulley 36, engage the pulley, and thence continue upwardly at an angle without the nacelle to the inner portions of the upper wings where they are fastened adjacent to the trailing edges of said wings. By movement of the control column toward the operator, a pull is exerted on the connections 35 (cables) and the angle of attack of the upper wings in consequence increased. This decrease in the gap between the superposed wings at the trailing edge increases the gap at the leading edge, varies the dcalage and accordingly effectually eliminates all tendency to nose dive incident to flight.

Fore and aft oscillation of the control column 32 is also instrumental in controlling the elevator flaps 22. The leads 36 for the elevators extend into the nacelle and are fastened respectively above and below and equidistantly from the axis of oscillation of said column. Both the elevator flaps 22 and the increased dcalage act conjointly in eliminating nose dive and effecting climb. Movement of the column to ward the aviator or pilot, simultaneously increases the decalage and actuates the e evator flaps. The elevator leads, it will be noted, cross, intermediate their ends.

-Manipulation of the rudder flaps 23 is obtained through operation of a control wheel 37 mounted at the free end of the control column 32 for rotation about a fore and aft axis. Rudder leads 38 extend from a drum 39 rotatable with the wheel 37 (its axis being alined with the axis of the wheel) over pulleys 40 mounted adjacent to the base of the column and thence rearwardly without the nacelle to the rudder flaps. By this arrangement the rudders may be operated independently of the elevator flaps or simultaneously should occasion demand.

In effecting an increase in the dcalage the air pressure upon the upper wing is utilized in addition to the leverage obtained through 244. AERONAUTICS manipulation of the control column. An increase in the angle of attack obviously increases the climbing efiiciency of the craft. Hence, a tendency to nose dive is completely eliminated by utilization of this increase in the angle of attack in connection with the righting tendency obtained through the simultaneous manipulation of the elevator flaps.

In the modification of the invention illustrated in Fig. 7 but a single set of directional control flaps are used. This construction is characteristic of the Dunne type machine. The said flaps (but one of which is shown) have been designated 41 and disposed at the tips of the lower wings. The upper wings are made warpable at their tips so that the angle of attack at said tips may be increased if desired. Leads 42 are provided for this purpose. By operation of one of the flaps 41, directional control in a lateral plane is effected; by operation of said flap simultaneously, directional control in a vertical plane is effected, and by operation of said flaps simultaneously and in conjunction with an increase in the angle of attack of the wing tips through manipulation of the leads 42, the climbing efficiency of the craft is increased and all nose diving tendency avoided.

In the modification illustrated in Fig. 8, a stop 43 is provided inside the nacelle and in such relation to the control column as to contact with the lever 44 (corresponding to the lever 34 in the preferred form) to limit its movement in one direction. Said lever 44 in this modification is mounted loose upon the control column shaft and angularly extended beyond the control column for contact with said stop. By this arrangement, oscillation of the column in one direction will carry the lever 44 with it and as a result exert the required pull on the connections to warp or increase the angle of attack of the upper wings. Movement, however, in the opposite direction is limited by the stop 43. Hence, variation in the dcalage is limited.

Although I have illustrated and described the application of the invention in connection with a Dunne type machine, no limitation is to be interpreted. Furthermore, reference herein to elevator flaps is intended to cover ailerons, warpable wing tips and equivalent control surfaces.

'What I claim is:

1. In an aircraft, a supporting surface, and means for varying the angle of attack of the center section of the supporting surface on opposite sides of and closely adjacent to the fore and aft center line thereof without correspondingly or otherwise varying the end portions.

2. In an aircraft, superposed supporting surfaces, and means for varying the angle of attack of the center section of oneof the supporting surfaces without correspondingly or otherwise varying either the end portions of the same supporting surface or any portion of the remaining supporting surface or surfaces.

3. In an aircraft, a supporting surface having a variable angle of attack, a propelling means, a hinged control surface mounted at one end of the supporting surface, control mechanism and connections respectively between the control mechanism and the control surface and the control mechanism and the supporting surface simultaneously moving the control surface and varying the angle of attack of the supporting surface by operation of said mechanism.

4. In an aircraft, a supporting surface, and a means for varying the angle of attack of the center section of the supportingsurface without correspondingly or otherwise varying the end portions thereof, the variation in the angle of attack of said center section being the same directionally on either side of the fore and aft center line of the machine.

5. In an aircraft, superposed supporting surfaces and means for varying the angle of attack of the center section of one of the supporting surfaces without correspondingly or otherwise varying the end portions thereof, the variation in the angle of attack in said center section being the same directionally and quantitatively on either side of the fore and aft center line of the machine.

6. In an aircraft, a supporting surface, a propelling means, and a means for altering the angle of attack of said supporting surface in the vicinity of the fore and aft axis of the craft without a corresponding alteration throughout the alteration in the angle of attack of the supporting surface being directionally and quantitatively the same on both sides of the fore and aft axis of the machine.

7. In an aircraft, superposed supporting surfaces, a propelling means, and a means for altering the angle of attack of one of said supporting surfaces in the vicinity of the fore and aft axis of the craft without correspondingly or otherwise altering the angle of attack of the end portions thereof and without correspondingly or otherwise altering the angle of attack of the other supporting surface.

8. In an aircraft, superposed supporting surfaces, a propelling means, and a means for varying the gap between said surfaces in the vicinity of the fore and aft axis of the craft without any variation whatsoever in the gap between the superposed supporting surfaces throughout the remaining portion or portions of their length.

9. In an aircraft, swept back supporting surfaces, a propelling means, and a means for varying the gap between said support ing surfaces in the vicinity of the apex formed thereby without a corresponding variation in the gap throughout.

10. In an aircraft, swept back supporting surfaces, a propelling means, a control surface, and a means operable through control movement of said control surface to alter the angle of attack of said supporting surface in the vicinity of the fore and aft axis of the craft without a corresponding alteration throughout.

11. In an aircraft, swept back superposed supporting surfaces, a propelling means, and segregated elevator flaps and rudders mounted respectively at the lower and upper wing tips.

12. In an aircraft, swept back superposed supporting surfaces, a propelling means, and segregated elevator flaps and rudders mounted respectively at the wing tips with the elevator flaps disposed lowermost and aft of said rudders.

13. In an aircraft, a swept back supporting surface, a propelling means, and means connecting with the beak of the swept back supporting surface for distorting a portion thereof in advance of a line passing transversely through the center of pressure without correspondingly or otherwise distorting any portion whatsoever of the supporting surface located to the rear of said line.

14. In an aircraft, swept back supporting surfaces of unequal span, said surfaces terminating rearwardly in unalined vertical planes, a propelling means and segregated elevator flaps and rudders mounted respectively at the tips of said supporting surfaces, the elevator fiaps being disposed aftermost.

15. In an aircraft, superposed supporting surfaces, a means for varying the gap between the supporting surfaces by alteration of the angle of attack of one of said surfaces, a control surface carried by one of the supporting surfaces, and unit control mechanism operable to simultaneously vary the angle of attack of the variable supporting surface and actuate said control surface.

angle of attack of the remaining portion or portions thereof, and means connecting with the supporting surface for opposing such variation in its angle of attack. 17. In an aircraft, a swept back'supporting surface having a normal angle of attack, control means for increasing the angle of attack of the central portion of said surface beyond normal, and means opposing said control means for returning said surface to its normal angle of attack the moment said control means is released.

18. In an aircraft, a supporting surface, the portion of said surface in the vicinity of the fore and aft axis of the machine having an axis of oscillation longitudinally of said surface and aft of the center of lift, the end portions of said surfaces being fixed, a propelling means, and a means yieldingly opposing the unbalancing moment on said surface in consequence of the location of its axis of oscillation aft of said center of lift.

19. In an aircraft, a supporting'surface, a portion of said surface lying in the fore and aft axis of the machine and having a variable angle of attack, an oscillatable control means for varying the angle of attack of said surface, and connections engageable with said control means at points distant from its axis of oscillation proportional to the degree of variation to be given that portion of the surface-to which theparticula connection is fastened. v

20. In an aircraft having... a swept back supporting surface, the beak portion of said surface being forward of the center of pressure and the end portions being aft thereof, and means for varying the angle of attack of said forward beak port'i'onindependently of said end portions thereof.

In testimony whereof I hereunto aflix signature.

WILLIAM STARLING BURGESS. 

